This is a randomized, multi center, double-masked, placebo-controlled study of recombinant human interleukin eleven (rhIL-11) in subjects with active Crohn's Disease. The objectives of this study are: PRIMARY 1. Assess the efficacy of rhIL-11 in subjects with active Crohn's disease who are not receiving prednisone therapy. 2. Evaluate the effect of varied rhIL-11 dosing schedules SECONDARY 1. Assess the safety of rhIL-11 in subjects with active Crohn's disease. 2. Assess the effect of varied rhIL-11 dosing schedules on subjects' quality of life. 3. Explore the potential of rhIL-11 treatment as a c cost-effective therapy for Crohn's disease